Only by examining a large number of tornado intercepts can Wurman learn the average dimensions, rotational velocity, speed of progression, life span, and more. A doctoral student named Curtis Alexander, whom Wurman is advising, has made a start. He has almost completed a climatological study of these winds based on most of Wurman’s 141 data sets.
Some of Alexander’s findings confound the experts. Take the ferocity of the winds. It had always been assumed that about 2 percent of tornadoes fall into the violent EF-4 and EF-5 categories on the Enhanced Fujita scale, which estimates wind force primarily on the evidence of damage to man-made structures. Alexander’s preliminary results suggest that these “town killers” account for a much larger portion—15 times larger, about 30 percent of the total. This would indicate that at least 300 potentially devastating tornadoes churn through the United States every year, nearly all unrecorded as they sweep through remote countryside.
“We would have thought that most were EF-0s, weak, and that you get fewer and fewer as they get stronger and stronger,” Wurman says. “But that’s not the case. It turns out that there are not many weak ones, mostly moderate ones, and a surprising number of violent ones.” At the moment, there is no explanation for this observation.
The amount we still do not know about tornadoes amazes Wurman, who recalls his 2005 encounter with an advancing supercell with two tornadoes in its midst. One was “single vortex, fairly smallish”; the other was “this big dust roll with multiple vortices.” He was stupefied that such different structures could arise under very similar conditions. “If it was something to do with the relative humidity or the temperature or the winds that day, then how did two different outcomes happen?” he asks. “I guess I was just in awe of my ignorance.”
Last year’s death toll of 125 from tornadoes in this country was the highest in a decade and the second-highest in more than 30 years. The reasons remain obscure. So it is apt that this May some 80 atmospheric scientists (including Bluestein and Wurman) will gather in Norman to engage in a five-week, military-style campaign of surround-and-conquer, adopting Wurman’s nomadic style and throwing everything they’ve got at solving the problem of tornado prediction.
“It is by far the most ambitious, largest tornado study that has ever happened,” Wurman says. “There is no comparison with any previous tornado project, really.” Named Vortex2, it is funded by the National Science Foundation and the National Oceanic and Atmospheric Administration with a budget of about $7 million, and it will extend over two spring seasons. Both Bluestein and Wurman are on the project’s eight-member steering committee.
The scale and logistics of Vortex2 are enormous. Some 30 vehicles will participate, including 10 mobile radar trucks, four weather-balloon launchers, and two vehicles bearing a total of four disdrometers (to measure the size distribution of rain or hail). In addition, 10 instrumented vehicles will form a mobile mesonet—a temporary automated network of weather stations. Fast-working crews will deploy and retrieve 36 probes, including two dozen Stick-Nets, tripod-mounted instruments, in and around tornadoes. Outfitted with anemometers, the probes will log wind speed and other information at ground level, a zone overshot by radar.
Erik Rasmussen, a prominent meteorologist who led the previous Vortex project, will use unmanned aircraft to record temperature and relative humidity at various altitudes. Other researchers will shoot storm videos for later analysis. Should there be direct tornado hits on towns, damage-survey teams will break off from the group to collect data on the impacted structures.
Never having collaborated before, Bluestein and Wurman will arrive at Vortex2 knowing that nothing short of a huge team effort will yield detailed portraits of tornadoes, their parent supercells, and nesting mesocyclones —the data needed to unravel the mystery that has surrounded tornadoes. “It’s more fun being out on your own than being told what to do,” Bluestein says. Still, he acknowledges, “in order to make what Josh and I have been doing more valuable, you must have a more complete time record of the entire storm.”
Adapting technologies invented for military defense, Bluestein and Wurman are now experimenting with phased array and rapid scan, or multibeam, radars, able to view a complete storm in 10 seconds. Once their analysis of the data from Vortex2 is complete, Wurman is optimistic that meteorologists will finally know why “some storms make big tornadoes versus small tornadoes, what causes a tornado to strengthen, what causes it to die.” The next time, he hopes, people on the ground will not have to wait and wonder what is about to hit, as they did in Greensburg. “We need to be able to tell forecasters, we need to be able to tell computer modelers what we’ve learned,” he says. A reliable one-hour tornado warning for families in the Midwest, Wurman says, would be “a great success.”
